ترغب بنشر مسار تعليمي؟ اضغط هنا

High-Pressure Electrical Resistivity Measurements of EuFe2As2 Single Crystals

122   0   0.0 ( 0 )
 نشر من قبل Nobuyuki Kurita
 تاريخ النشر 2010
  مجال البحث فيزياء
والبحث باللغة English




اسأل ChatGPT حول البحث

High-pressure electrical resistivity measurements up to 3.0GPa have been performed on EuFe2As2 single crystals with residual resistivity ratios RRR=7 and 15. At ambient pressure, a magnetic / structural transition related to FeAs-layers is observed at T0 =190K and 194K for samples with RRR=7 and 15, respectively. Application of hydrostatic pressure suppresses T0, and then induces similar superconducting behavior in the samples with different RRR values. However, the critical pressure 2.7GPa, where T0=0, for the samples with RRR=15 is slightly but distinctly larger than 2.5GPa for the samples with RRR=7.



قيم البحث

اقرأ أيضاً

We have grown single crystals of EuFe2As2 and investigated its electrical transport and thermodynamic properties. Electrical resistivity and specific heat measurements clearly establish the intrinsic nature of magnetic phase transitions at 20 K and 1 95 K. While the high temperature phase transition is associated with the itinerant moment of Fe, the low temperature phase transition is due to magnetic order of localized Eu-moments. Band structure calculations point out a very close similarity of the electronic structure with SrFe2As2. Magnetically, the Eu and Fe2As2 sublattice are nearly de-coupled.
We have constructed a pressure$-$temperature ($P-T$) phase diagram of $P$-induced superconductivity in EuFe$_2$As$_2$ single crystals, via resistivity ($rho$) measurements up to 3.2 GPa. As hydrostatic pressure is applied, an antiferromagnetic (AF) t ransition attributed to the FeAs layers at $T_mathrm{0}$ shifts to lower temperatures, and the corresponding resistive anomaly becomes undetectable for $P$ $ge$ 2.5 GPa. This suggests that the critical pressure $P_mathrm{c}$ where $T_mathrm{0}$ becomes zero is about 2.5 GPa. We have found that the AF order of the Eu$^{2+}$ moments survives up to 3.2 GPa without significant changes in the AF ordering temperature $T_mathrm{N}$. The superconducting (SC) ground state with a sharp transition to zero resistivity at $T_mathrm{c}$ $sim$ 30 K, indicative of bulk superconductivity, emerges in a pressure range from $P_mathrm{c}$ $sim$ 2.5 GPa to $sim$ 3.0 GPa. At pressures close to but outside the SC phase, the $rho(T)$ curve shows a partial SC transition (i.e., zero resistivity is not attained) followed by a reentrant-like hump at approximately $T_mathrm{N}$ with decreasing temperature. When nonhydrostatic pressure with a uniaxial-like strain component is applied using a solid pressure medium, the partial superconductivity is continuously observed in a wide pressure range from 1.1 GPa to 3.2 GPa.
216 - X. F. Wang , T. Wu , G. Wu 2009
Sizable single crystals of $BaFe_2As_2$ have been grown with self-flux method. The crystals are plate-like with c-axis perpendicular to the plane. The size can be as large as 3 x 5 x 0.2 $mm^3$. The resistivity anisotropy ($rho_c/rho_{ab}$) is as lar ge as about 150, and independent of temperature. The transport in ab plane and along c-axis direction shares the same scattering mechanism. In contrast to the magnetic behavior of polycrystalline samples, no Curie-Weiss behavior are observed, a temperature linear dependent susceptibility occurs above spin-density-wave (SDW) transition. The susceptibility behavior is very similar to that of antiferromagnetic SDW chromium. Magnetic behavior of single crystal definitely gives evidence for existence of local moment except for the contribution to susceptibility from itinerant electrons. A resistivity minimum strongly dependent on magnetic field is observed. A log(1/T) divergency, similar to that of the underdoped cuprates, happens at low temperature. Here we first present intrinsic transport and magnetic properties, and their anisotropy from high quality single crystal.
In this work, fabrication and characterization of magnetic properties of EuFe2As2 and EuRbFe4As4 single crystals is reported. Magnetization measurements of samples with well defined thin film geometry and crystal orientation demonstrate a striking si milarity in ferromagnetic properties of Eu subsystems in these two compounds. Measurements with magnetic field applied along ab crystal planes reveal meta-magnetic transition in both compounds. Numerical studies employing the Jz1-Jz2 Heisenberg model suggest that the ground state of the magnetic order in Eu subsystem for both compounds is the helical spin order with the helical angle about 2pi/5, while the meta-magnetic transition is the helix-to-fan first order phase transition.
Resistivity and Hall effect measurements of EuFe$_2$As$_2$ up to 3.2,GPa indicate no divergence of quasiparticle effective mass at the pressure $P_mathrm{c}$ where the magnetic and structural transition disappears. This is corroborated by analysis of the temperature ($T$) dependence of the upper critical field. $T$-linear resistivity is observed at pressures slightly above $P_mathrm{c}$. The scattering rates for both electrons and holes are shown to be approximately $T$-linear. When a field is applied, a $T^2$ dependence is recovered, indicating that the origin of the $T$-linear dependence is spin fluctuations.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا